The present invention relates to apparatus for measuring the processing temperature of workpieces. The invention is particularly useful for measuring the processing temperature of semiconductor wafers and is therefore described below with respect to this application, but it will be appreciated that the invention could be advantageously used also in other applications.
The in situ temperature measurement of semiconductor wafers during their processing may be of critical importance as certain processing operations must be performed at precisely controlled temperatures. One method of measuring the processing temperature is by the use of thermocouples in heat-conducting relation with the wafers. However, such thermocouples may interfere with the processing of the wafer, disturb the temperature distribution on the wafer, and/or hinder the handling of the wafer.
Optical methods for wafer temperature measurement are well known but their accuracy may be affected by environmental conditions, such as stray radiation or wafer emissivity during the thermal processing of the wafer.